The short version

You'll probably also want to check out the branch for whatever stable version of Mahara you're using. For instance, if you're on Mahara 15.04, you would do:

git checkout 15.04_STABLE

The long version

Git

The Mahara Project source code is managed using the Git distributed version control system. In the normal Git workflow, developers "clone" the Mahara project Git repository, which means they have their own full copy of the source code including all branches and history. So if any or all of the official Git repo's listed below were to go away, the project could always be restarted from a single dev's copy of the repo.

If you haven't used Git before, well, it does have a nasty learning curve. Taking a couple of hours to go over a Git tutorial that covers the underlying concepts (preferably something that includes the phrase "directed acyclic graph") is highly recommended.

Branches & Tags

Mahara maintains one branch for each major version of Mahara. For a major verison X.Y, the corresponding branch will be X.Y_STABLE. For instance, Mahara 15.04 is in branch 15.04_STABLE, 1.7 is in 1.7_STABLE, etc.

Minor releases are marked by tags. Release X.Y.Z will be marked with tag X.Y.Z_RELEASE.

Additionally, there is a "master" branch which contains development work on the next major release that has not been released yet.

reviews.mahara.org

At present the "live" version of the code base is in the git repository of our Gerrit code review system, https://reviews.mahara.org . The code here is usually updated by people pushing patches into Gerrit, where they are reviewed and merged by Mahara core developers. Users with the right permissions can also push patches directly to this git repo, and this happens occasionally as well (for instance the version bumps that are done by the scripts that package up our releases).

Synced git repositories

The Mahara Gerrit site automatically replicates all changes into our repositories in several locations in near realtime. If you are going to clone the Mahara repository, it's preferred that you clone it from one of these sites rather than from https://reviews.mahara.org, in order to reduce the load on our Gerrit server.

Third-party plugins

Mahara is quite pluggable, and there are many third-party plugins available for Mahara. Third-party plugin authors each have their own code repositories, often on Github. There was formerly a "mahara-contrib" repository in the Mahara project on Gitorious, but it's no longer in active use.